1. Field of the Invention
The present invention relates to an enzyme having an action of synthesizing from sucrose a biologically active polysaccharide RON substance (hereinafter referred to as "RON substance" according to circumstances) having excellent antitumor activity, immunomodulating activity and host defense activity against infectious diseases, and a process for producing this RON substance by using this enzyme.
2. Description of the Related Art
The RON substance intended in the present invention and a process for extracting this RON substance from rice bran have already been disclosed in Japanese Patent Publication No. 62-7173 (which corresponds to U.S. Pat. No. 4,762,825).
According to this conventional process, the RON substance is extracted from rice bran and the extract is purified. Therefore, the quality of the starting material is unstable, and there are considerable dispersions of the physicochemical properties and biologically activities of the obtained substance. Moreover, the yield is low and many steps are required, and the conventional process involves the problem of long operation time and is economically disadvantageous.